Blasting with safety fuse



Ap 1941- J. B. STONEKING 2,239,123

BLASIING WITH SAFETY FUSE Filed March 1, 1939 INVENTOR JAY a. STONEK/NG Patented Apr. 22, 1941 BLASTING WITH SAFETY FUSE Jay B. Stoneking, Livermore, Calm, assignor to The Ensign-Bickford Company,

Simsbury,

001111., a corporation of Connecticut Application March 1, 1939, Serial No. 259,135

4 Claims.

My present invention relates to the art of setting off explosive charges, as-in mining, military uses, and in pyrotechnic displays, and aims to provide certain improvements therein. More especially, it relates to an improved system of setting off one or more explosive charges of a blasting round or a pyrotechnic display with greater safety, efiiciency and convenience.

Blasting, especially in mine use, is most usually carried out with either black powder or high explosive. Where black powder is employed the conventional practice is to connect to the explosive charge a piece of safety fuse long enough to reach beyond the mouth of the hole in which the charge is inserted. Of course, the charges are tamped down into the holes in the conventional manner before the end of the fuse is ignited, and since fuse burns, usually at the rate of one and onehalf feet to two feet per minute, the miner requires a sufficient length of safety fuse to allow him to reach a place of safety after ignition. Where high explosives are used they are fired either by safety fuse and a detonating cap, or by electric fusee. Where a detonating cap and safety fuse aroused, the cap is crimped tight onto the end of the fuse and embedded in the cartridge, and upon being exploded by fire from the fuse, detonates the charge. In both these methods of blasting, the miner or miners are at the working face whereat the charges are to be set off. Where rotational firing is to be carried out each charge must have an individual fuse which must be ignited separately, hence a considerable amount of fuse must be employed to allow the miner to reach a place of safety after the fuses are ignited.

According to my invention an entire series or round of explosive charges may be ignited by one man stationed at a safe distance from the charges of explosives by the application of a flame to a single point. To accomplish this my invention resides in connecting a so-called ignition cord to the fuse or fuses in a suitable manner, such as by wrapping it around each fuse at a point where the powder core of the fuse has been exposed, and then extendin the free end of the ignition cord to any desired distance from the scene of the blast, at which point the ignition cord will be severed from its supply and the free end of the connected cord ignited, which, in turn, will ignite the safety fuse or fuses which provide the fire for the ignitable powder or blasting caps. The ignition cord which I propose to use is a joint invention of David E. Pearsall and John D. Rich,

which is described and claimed in a co-pending covering for said central element that will provide a firm base for carrying a combustible medium, which will burn at a substantially uniform rate and project a regulated flame from its surface but will not disturb the position or arrangement of the supporting element and which will remain firmly in place after the fire has passed, although it may be partly demolished by the force of the subsequent explosion. The ignition oord can be ignited by a match or any means capable of producing a flame, sparks, or even by a heated element, and will burn at a rate that may be controlled between limits of approximately one foot in one second to one foot in twenty seconds,

. and the projected flame is of such character as to be capable of igniting safety fuse or other devices to which it may be attached.

The invention will be better understood from the further detailed description when considered in connection with the accompanying drawing showing an application of my invention, and wherein-- Figure 1 represents an elevation of a mine face showing the location of the various drilled holes and one manner in which they may be fired.

Fig. 2 is a section taken substantially along the plane of the line 22 of Fig. 1. 1

Referring to the drawing, the mine face is a tunnel or cavity l0 having a working face H which latter is to be extended. To accomplish this there is drilled into the mine face H in conventional manner a plurality of holes l2, l3, M, I5, l6 and I], which holes are to be consecutively fired in the order of their numbers. Each of the holes is charged with explosive Hi which may be either black powder, dynamite or the like, and extending from each of these charges is a length or section of safety fuse by means of which the charge may be exploded. I have herein shown the fuses 19 extending from the holes is to i? as being safety fuse, whereas those indicated by the reference numeral 20 extending from the holes I2, are detonating fuse.

As above stated, the various blasting charges are to be set off in the order of their numerals from a point at a safe distance from the mine face and by the application of a flame to a single point. To accomplish this the free ends of the various fuses are connected by lengths of ignition cord 2| of the character described, by winding a section of the cord around the free ends of the fuses in a manner such that the flame propagated by the ignition cord will contact and ignite the powder cores of said fuses. The timing or rotation of the blasts is accomplished by the ignition cords and is dependent upon the effective length of the ignition cord from the point of contact with the-fuses to the point of application of the flame to the ignition cord.

To secure simultaneou ignition of two or more blasting charges, the customary safety fuse and caps are omitted and these individual fuses are replaced by lines of ,detonating fuse such as 20, extending into the explosives charges and projecting from same for a distance sufficient to permit them to be connected or bound to each other, as indicated at 22, and to the capped end of a safety fuse 19', which is, in turn, attached to the ignition cord 2|.

Thus it will be apparent that any desired manner of blasting may be accomplished by the proper combination of the rotational and simultaneous methods of connecting the ignition cord with the fuses which are attached to the blasting charges. In any or all of these methods, however, the initial ignition is accomplished by the single application of a flame or glow at only one point of the ignition cord, which, in the example illustrated, is at the free end of the length of ignition cord M which is connected to the free end of the safety fuse IS.

The method here described ofiers possibilities for economies because the safety fuses used in the blast may be shorter than are required by conventional practice in that, in accordance with the present invention they will extend just sufficiently away from the explosives to permit safe and satisfactory connection, and their time factor will be taken care of or provided for by the length of ignition cord connected to said fuses.

In this connection it will be apparent that the rate of burning of the ignition cord is much faster than that of the safety fuse and that the time of burning of a length of safety fuse used, will be greater than the time of burning of the length v of ignition cord remaining unburned at the time of ignition of the first fuse end employed in setting off the round of blasting charges.

From the foregoing detailed description it will be appreciated that arrangements for connection with blasting charges other than that here illustrated and described may be resorted to, the primary conditions being the rotational order in which the charges are to be set off and the factors of safety and economy to be followed.

I have not herein specifically illustrated the actual construction of ignition cord to be used since my invention in its primary concept may be used with any ignition cord or device which has the property of projecting a regulated flame from its surface, of a character such as to ignite safety fuse to which it is attached.

What I claim is:

1. A system of securing rotational firing of a round of blasting charges or a pyrotechnic display in any desired order from a safe distance away, which comprises attaching to the free ends of approximately equal lengths of safety fuse connected to the respective charges, an ignition cord which burns at a definite rate which is much faster than the burning rate of the safety fuse and projects a regulated fiame from its surface while burning, using lengths of safety fuse such that the time of burning of one length thereof will be greater than the time of burning of the portion of ignition cord that remainsunburned at the time of ignition of the first fuse end, so

g fuse ends by igniting the ignition cord ata point in advance of the first charge to be set ofl.

2. A system of securing the rotational firing of a round of blasting charges or a pyrotechnic display in any desired order from a safe distance away, which comprises attaching to the free ends of approximately equal lengths of safety fuse connected to the respective charges, lengths of ignition cord which burn at a definite rate which is much faster than the burning rate of the safety fuse and project a regulated flame from their surface while burning, using lengths of safety fuse such that the time of burning of one length thereof will be greater than the time of burning of the lengths of the ignition cord between the first and last fuse ends employed in setting off the round of blasting charges, so arranging the order of attachment of the safety fuse ends to the ignition cords that the lengths of said ignition cords between the ends of the safety fuse and the point at which the cord is ignited will be the determining factor of the order of setting off the charges, connecting said ignition cords together in a manner to provide a continuous length of ignition cord from each safety fuse to a point in advance of the charge tobe first set off, and igniting the ignition cord at such point.

3. An ignition assembly for setting off a round of blasting charges or a pyrotechnic display in any desired order from a single point remote from the charges, which comprises a plurality of blasting charges, approximately equal lengths of safety fuse connected to each of the respective charges, an ignition cord which burns at a dellnite rate which is much faster than the burning rate of the safety fuse and projects a flame from its surface when burning connected to the exposed ends of the safety fuses, the lengths of the safety fuse being such that the timeof burning of one length will be greater than the time of burning of the entire length of ignition cord between the first and last fuse ends employed in setting off the round of blasting charges, and the effective lengths of the ignition cord between the ends of the safety fuse and the point at which the ignition cord is to be ignited, being the determining factor of the time order in which the charges are to be set off.

4. An ignition assembly for setting off a round of blasting charges or a pyrotechnic display in any desired order from a single point remote from the charges, which comprises a plurality of blast ing charges, approximately equal lengths of safety fuse connected to each of the respective charges, a pliable ignition cord so constructed that it can be bent into any desired shape or position and remain so fixed during burning and which burns at a definite rate which is much faster than the burning rate of the safety fuse and projects a flame from its surface when burning connected to the exposed ends of the safety fuses, the lengths of the safety fuse being such that the time of burning of one length will be greater than the time of burning of the entire length of ignition cord between the first and last safety fuse ends employed in setting off the round of blasting charges, and the effective lengths of the ignition cord between the ends of the safety fuse and the point at which the ignition cord is to be ignited, being the determining factor of the time order in which the charges are to be set off.

JAY B. STONEKING. 

